Commit 4c466872 authored by Enric Balletbo i Serra's avatar Enric Balletbo i Serra Committed by Alexandre Belloni
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rtc: bq32000: add support to enable disable the trickle charge FET bypass 



The bq32000 includes a trickle charge circuit to maintain the charge of the
backup supply when a super capacitor is used.

You can enable the charging circuit by setting 'trickle-resistor-ohms',
additionally you can set TCFE to 1 to bypass the internal diode and boost
the charge voltage of the backup supply. You might want to enable/disable
the TCFE switch from userspace (e.g when device is only connected to a
battery)

This patch introduces a new sysfs entry to enable and disable this FET
form userspace.

Signed-off-by: default avatarEnric Balletbo i Serra <enric.balletbo@collabora.com>
Signed-off-by: default avatarAlexandre Belloni <alexandre.belloni@free-electrons.com>
parent 5dff3a31

Documentation/ABI/testing/sysfs-bus-i2c-devices-bq32k

0 → 100644
+7 −0
Original line number Diff line number Diff line 
What:		/sys/bus/i2c/devices/.../trickle_charge_bypass

Date:		Jan 2017

KernelVersion:	4.11

Contact:	Enric Balletbo i Serra <eballetbo@gmail.com>

Description:    Attribute for enable/disable the trickle charge bypass

		The trickle_charge_bypass attribute allows the userspace to

                enable/disable the Trickle charge FET bypass.

drivers/rtc/rtc-bq32k.c

+76 −0
Original line number Diff line number Diff line
@@ -34,6 +34,7 @@ 
#define BQ32K_CALIBRATION	0x07	/* CAL_CFG1, calibration and control */

#define BQ32K_TCH2		0x08	/* Trickle charge enable */

#define BQ32K_CFG2		0x09	/* Trickle charger control */

#define BQ32K_TCFE		BIT(6)	/* Trickle charge FET bypass */



struct bq32k_regs {

	uint8_t		seconds;
@@ -188,6 +189,65 @@ static int trickle_charger_of_init(struct device *dev, struct device_node *node) 
	return 0;

}



static ssize_t bq32k_sysfs_show_tricklecharge_bypass(struct device *dev,

					       struct device_attribute *attr,

					       char *buf)

{

	int reg, error;



	error = bq32k_read(dev, &reg, BQ32K_CFG2, 1);

	if (error)

		return error;



	return sprintf(buf, "%d\n", (reg & BQ32K_TCFE) ? 1 : 0);

}



static ssize_t bq32k_sysfs_store_tricklecharge_bypass(struct device *dev,

						struct device_attribute *attr,

						const char *buf, size_t count)

{

	int reg, enable, error;



	if (kstrtoint(buf, 0, &enable))

		return -EINVAL;



	error = bq32k_read(dev, &reg, BQ32K_CFG2, 1);

	if (error)

		return error;



	if (enable) {

		reg |= BQ32K_TCFE;

		error = bq32k_write(dev, &reg, BQ32K_CFG2, 1);

		if (error)

			return error;



		dev_info(dev, "Enabled trickle charge FET bypass.\n");

	} else {

		reg &= ~BQ32K_TCFE;

		error = bq32k_write(dev, &reg, BQ32K_CFG2, 1);

		if (error)

			return error;



		dev_info(dev, "Disabled trickle charge FET bypass.\n");

	}



	return count;

}



static DEVICE_ATTR(trickle_charge_bypass, 0644,

		   bq32k_sysfs_show_tricklecharge_bypass,

		   bq32k_sysfs_store_tricklecharge_bypass);



static int bq32k_sysfs_register(struct device *dev)

{

	return device_create_file(dev, &dev_attr_trickle_charge_bypass);

}



static void bq32k_sysfs_unregister(struct device *dev)

{

	device_remove_file(dev, &dev_attr_trickle_charge_bypass);

}



static int bq32k_probe(struct i2c_client *client,

				const struct i2c_device_id *id)

{
@@ -224,11 +284,26 @@ static int bq32k_probe(struct i2c_client *client, 
	if (IS_ERR(rtc))

		return PTR_ERR(rtc);



	error = bq32k_sysfs_register(&client->dev);

	if (error) {

		dev_err(&client->dev,

			"Unable to create sysfs entries for rtc bq32000\n");

		return error;

	}





	i2c_set_clientdata(client, rtc);



	return 0;

}



static int bq32k_remove(struct i2c_client *client)

{

	bq32k_sysfs_unregister(&client->dev);



	return 0;

}



static const struct i2c_device_id bq32k_id[] = {

	{ "bq32000", 0 },

	{ }
@@ -240,6 +315,7 @@ static struct i2c_driver bq32k_driver = { 
		.name	= "bq32k",

	},

	.probe		= bq32k_probe,

	.remove		= bq32k_remove,

	.id_table	= bq32k_id,

};

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